Prevalence and risk factors of drug-resistant extrapulmonary tuberculosis

Background Physicians are usually aware of the occurrence of drug-resistant (DR) pulmonary tuberculosis (PTB), but lack concern about DR-extrapulmonary TB (EPTB). Data regarding the prevalence and risk factors of DR-EPTB remain limited. Objectives To determine the prevalence and risk factors of DR-EPTB. Methods A retrospective study was performed in patients who had culture-proven Mycobacterium tuberculosis (MTB) from various specimens between January 2013 and December 2015. Patients were classified into three groups: PTB, EPTB and concomitant PTB and EPTB (PTB + EPTB). Clinical data, chest radiographic extent of disease and patterns of DR were collected. Results There were 1014 culture-proven MTB specimens (716 pulmonary specimens and 298 extrapulmonary specimens) from 986 patients (648 PTB, 218 EPTB and 120 PTB + EPTB). The prevalences of isoniazid-, rifampicin- and multidrug-resistant EPTB were 7.8%, .5% and .5%, respectively, which were lower than those of PTB. When PTB and EPTB coexisted, a higher rate of DR-TB was observed than for PTB alone. Of 338 EPTB patients, the extent of radiographic disease was associated with isoniazid-, rifampicin- and multidrug-resistant TB. Previous history of TB and use of steroids/immunosuppressive drugs were also associated with rifampicin- and multidrug-resistant TB in multivariate analysis. Conclusions The prevalence of DR-EPTB was high in patients who had concomitant PTB. Although the prevalences of rifampicin- and multidrug-resistant TB were low in isolated EPTB, the prevalence of isoniazid-resistant TB remained high. Therefore, drug susceptibility testing should be performed in EPTB patients, especially those who carry the aforementioned risk factors.